Pumps that transfer fluids can come in a variety of configurations. For example, one such type of pump is a gear pump. Gear pumps are positive displacement pumps (or fixed displacement), i.e. they pump a constant amount of fluid per each rotation and they are particularly suited for pumping high viscosity fluids such as crude oil. Gear pumps typically comprise a casing (or housing) having a cavity in which a pair of gears are arranged, one of which is known as a drive gear that is driven by a driveshaft attached to an external driver such as an engine or an electric motor, and the other of which is known as a driven gear (or idler gear) that meshes with the drive gear. Gear pumps in which both gears are externally toothed are referred to as external gear pumps. External gear pumps typically use spur, helical, or herringbone gears, depending on the intended application. Related art external gear pumps are equipped with one drive gear and one driven gear. When the drive gear attached to a rotor is rotatably driven by an engine or an electric motor, the drive gear meshes with and turns the driven gear. This rotary motion of the drive and driven gears carries fluid from the inlet of the pump to the outlet of the pump. In the above related art pumps, the fluid driver consists of the engine or electric motor and the pair of gears.
However, as gear teeth of the fluid drivers interlock with each other in order for the drive gear to turn the driven gear, the gear teeth grind against each other and contamination problems can arise in the system, whether it is in an open or closed fluid system, due to sheared materials from the grinding gears and/or contamination from other sources. The contamination in closed-loop systems is especially troublesome because the system fluid is recirculated without first going to a reservoir. These sheared materials are known to be detrimental to the functionality of the system, e.g., a hydraulic system, in which the gear pump operates. Sheared materials can be dispersed in the fluid, travel through the system, and damage crucial operative components, such as O-rings and bearings. It is believed that a majority of pumps fail due to contamination issues, e.g., in hydraulic systems. If the drive gear or the drive shaft fails due to a contamination issue, the whole system, e.g., the entire hydraulic system, could fail. Thus, known driver-driven gear pump configurations, which function to pump fluid as discussed above, have undesirable drawbacks due to the contamination problems.
In addition, the related-art systems are configured such that the prime mover (e.g., electric motor) is disposed outside the pump and a shaft extends through the pump casing to couple the motor to the drive gear. The opening in the casing for the shaft, while sealed to prevent fluid from leaking out, can still be a source of contamination. Also, related-art pumps have storage devices, e.g., accumulators, that are disposed separately from the pumps. These systems have interconnecting hoses and/or pipes between the pump and storage device, which introduce additional sources of contamination and increase the complexity of the system design.
Further, with respect to the internal pump configuration, the related-art gear pumps have bearing blocks that are configured to receive the shafts of the gears. The bearing blocks align the two gears such that the center axes of the gears are aligned with each other, such that the intermeshing of the gear teeth of the respective gears is to within an operational tolerance. However, because the bearing blocks in related-art pumps are separate components, seals and/or O-rings must be placed between each block and the corresponding pump casing, which adds to the complexity and weight of the pump assembly and also means more components that can fail.
Related-art systems do not solve the above-identified problems, especially in pumps used in industrial applications such as hydraulic systems. U.S. Patent Application Publication No. 2002/0009368 shows the use of independently driven motors to protect gear tooth surfaces from wear and excess stress in high-torque systems or systems with filler materials in the fluid. However, the motors in the '368 publication are external to the pump and thus would not eliminate all sources of contamination. In addition, the '368 publication does not teach to integrate the pump/prime mover and/or a storage device (e.g., an accumulator) to reduce or eliminate sources of contamination due to interconnections and an external motor configuration. Another related-art publication, WO 2011/035971, discloses a system in which a pump is integrated with a motor. However, the system in the '971 publication is a driver-driven system that can still introduce contamination due to the meshing of gears as discussed above. In addition, the '971 publication does not teach to integrate the pump and a storage device (e.g., an accumulator) to reduce or eliminate sources of contamination due to interconnections. Indeed, this concept is not even applicable because the fluid, i.e., fuel or mixture of urea and water, is consumed by the system and thus not recirculated. Therefore, any contamination has minimal impact, if any, as compared to, e.g., either a closed-loop or open-loop hydraulic system in which the fluid is recirculated. Further, the fuel pump and urea/water pump applications disclosed in the '971 publication are not comparable to the pressures and flows of a typical industrial hydraulics application such as, e.g., an actuator system that operates a boom of an excavator.
Further limitation and disadvantages of conventional, traditional, and proposed approaches will become apparent to one skilled in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present disclosure with reference to the drawings.